1. Field of the Invention
The invention relates to a glass roll, a product comprising a glass roll, as well as a device and a method for manufacturing the glass roll.
2. Description of Related Art
Designated as ultra-thin glasses are glasses having a thickness of less than approximately 300 μm, which bend easily, similar to glass fibers, due to their minimal thickness and, in fact, can be wound up to form glass on a roll. The smaller the thickness of the glass is, the more compactly the ultra-thin glass can be wound up. These kinds of glass rolls can comprise several 100s of meters of a glass ribbon. Great advantages result in the further processing of a glass roll in comparison to the processing of sheets, since cutting waste due to sheet size that has not been specified in advance is eliminated. Further, no additional transfer module, such as, e.g., a carrier, is required for supporting the very flexible thin glass sheets.
Ultra-thin glasses have come into use in numerous applications in recent years, in particular, in displays for flat screens or in contact-sensitive displays for tablet computers and smartphones, or also as substrate glasses for OLEDs. Additional products in which thin and ultra-thin glass can be used are, e.g., interposers, thin-film batteries, or capacitors.
By way of example, let us name WO 2011/014606 and US 2010/0260964, in which such glass rolls are disclosed. In WO 2011/014606, it is proposed to coat the two edge regions of a glass ribbon along the lengthwise edges with a flexible material, which projects laterally at least 1 mm beyond the glass ribbon, and which is used for handling the glass ribbon during further processing. The flexible region of the ribbon can have markings or a perforation for the transport and for the positioning of the glass ribbon during the further processing. In US 2010/0260964, it is proposed to laminate a support strip onto one surface of a glass ribbon, this strip projecting out beyond the glass ribbon to provide the other surface of the ribbon with a peelable protective film, and to roll up the laminate that is formed into a glass roll.
During the manufacture of ultra-thin glasses, defect sites of different types may occur, such as, for example, inclusions of bubbles, devitrifications, or inclusions of foreign material, which can result, for example, from batch remnants or tub material. At the present time, individual sheets of special glass or thin glass having defect sites of different types are usually rejected during the manufacture of sheets. For example, in DE 10 2012 002174 A1, a device and a method are disclosed for recognizing defect sites, whereby defect sites of the thin glass affected by defects are sorted out and discarded as rejects. However, in the manufacture of a glass roll, this can lead to the fact that a large quantity of defect-free glass ribbon is also discarded.
Likewise, the glass ribbon can be later subjected to an inspection for defects when the glass roll is unrolled, for example, within the course of a further processing of the glass roll, in which sheets of a prespecified glass roll are to be separated from the glass ribbon. The glass ribbon therefore runs through a defect inspection unit and the defect inspection unit transfers the information on the position of the defect on the glass ribbon to a computer, which calculates optimal cutting positions based on this information as well as the dimensions of sheets to be cut therefrom, and transmits these positions to a cutting unit, which is placed downstream from the defect inspection unit. The cuts are optimized in this way, so that a maximum number of sheets free of defects or with few defects can be manufactured from the continuous ribbon. Sites associated with defects can be cut out. However, it is a disadvantage that only the path between the defect inspection unit and the separating or cutting device is available for optimizing the cutting positions. Therefore, the optimizing can only be conducted over a locally confined region.
Frequently, contaminants of the glass ribbon that are removable, in contrast to defect sites of the glass ribbon, can be distinguished only with difficulty from defect sites in the glass ribbon by the inspection units. Therefore, it may happen that a segment of the glass ribbon containing a contaminant may be erroneously discarded as waste.